NASA has pushed back the date of its next crewed mission to the Moon yet again, amid fears China could outpace the US to the lunar south pole.
Bill Nelson, who leads Nasa, has been vocal of his fears should China beat the US to the Moon.
"My concern would be if China got there first and said, 'This is our territory, you stay out'," he told a committee hearing earlier this year, which intended to approve Nasa's $25.4bn (£20.3bn) budget request for 2025.
"Obviously you don't want to interfere with each other but don't declare that this whole territory is suddenly yours."
Artemis is Nasa's Moon campaign, and involves four uncrewed and astronaut-assisted missions.
In January, Nasa said the next mission, Artemis II, would launch in September 2025 instead of late 2024.
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Now the space agency has confirmed it is targeting a launch in April 2026.
The extension is supposed to lend time to engineers trying to fix issues with its next-generation Orion space capsule.
The uncrewed Artemis I flight in Orion in 2022 revealed the capsule posed "significant risks" after its heat shield wore away in more than 100 places.
The delay ultimately pushes back the Artemis III mission, which aims to land astronauts near the Moon's south pole.
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Instead of launching in September 2026, that mission is now planned for mid-2027.
The Artemis III mission forms parts of a decade-long programme that is hoped to culminate with a permanent lunar base by the end of the decade.
Nelson has said the adjusted timeline should still allow the US to reach the lunar surface before its space faring rival.
It is vital for us to land on the south pole so that we do not cede portions of that lunar south pole to the Chinese.
Nasa administrator, Bill Nelson
The mid-2027 goal “will be well ahead of the Chinese government’s announced intention," he said.
The Nasa boss added: “It is vital for us to land on the south pole so that we do not cede portions of that lunar south pole to the Chinese."
China plans to ferry its own astronauts to the lunar south pole in 2030.
In June, the country successfully landed its Chang'e-6 lunar probe on the moon's far "dark side" - a significant step in its three-part journey to gather data that will allow astronauts to return to the Moon in six years.
The south pole is, scientists believe, the most promising location for water-based ice, which will be key to future human habitation on the Moon.
The region is also one of the Moon's most resource-dense areas.
Experts believe 'cold traps' dotted on lunar surface contain gases like Helium-3, which can help produce huge amounts of energy on Earth.
Estimates suggest there could be between one and three million tons of Helium-3 on the Moon's outer layers - making it relatively easy to extract.
Yet, the precious gas accounts for about 0.0001% of helium on Earth.
Just one gram of Helium-3 would cost about $1,400, according to the Lunar and Planetary Institute, a research organisation founded in 1978.
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That means one ton would be worth around $1.26billion - and three million tons would be worth $3.78trillion.
Scientists estimate that just 25tons of Helium-3 could power the US for an entire year.
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